I don't have an apple developer license but I've dicked with the sdk and a few apps before.
It's not just a matter of creating an app. A bit of work would need to be done on the GG site itself. The app would need an API to communicate with the server, send requests, receive large quantities of structured data, etc.

XML seems like a logical choice for it, in the future non-apple devices could access that same API in apps made for them(android or something).

so:
- First you'd need to know exactly what you wanted the app to do, every single possible thing it would need to communicate with GG for.
- Formulate XML schemas that describe these requests and their possible responses.
- Find some chump to spend a few weeks of their spare time cutting code on the GG site so that it can parse requests, then build and serve responses as described by the XML schemas.
- Find some other chump to actually develop the app, which will be a lot more complicated than what needs to be done on the GG site.